Low flow through S600

[landlockeddivingdoc]

After a couple of dives with it, my fiance told me that her scuba pro s600 seemed hard to breathe through. The reg was serviced last fall, and I tried breathing through her setup (mk25) with a full tank, and it did seem sluggish compared to my g260 on a mk17.

I put an IP gauge on it, as well as measuring cracking pressure. IP is at 135 with no significant drift or creep, and a drop of 12 to 15 psi when purged. Cracking pressure is 1.0in with the balance knob fully open; I used an inline adjusting tool, as well as a screwdriver on the balance chamber, and that was pretty much the best that I could get as far as cracking pressure.

Thing is, initiation of the breath does seem easy--comparable to the g260 which has similar numbers. But after the air starts flowing, it seems like I have to inhale more forcefully to get a full breath, even with the Venturi assist operational.

I went ahead and connected the g260 to her first stage and hose, and after confirming all the numbers, it seems to be working as well as it did on the mark 17. So I think that this is probably in the second stage itself.

I removed the cover and inspected everything that I could, didn't see any debris, corrosion, etc. I haven't removed the barrel yet, since I need to go get a stronger pick to remove the stupid retaining clip. Maybe this is all in our heads, but I doubt it because several people have noticed it. Before I go looking for somebody with a flow meter (service center is several hours away), what more should I check in the second stage (The only things I can think of off hand were making sure that the seat isn't sticking/ the valve rings are gliding smoothly)?

I appreciate any suggestions in terms of understanding and correcting this issue.

 

[Pearlman]

With a cracking pressure of 1.0 it shouldn’t be hard to breathe from…

I had a silly issue (in restrospect) on my last vacation where my s600 was inexplicably hard to breath from and it tuned out to be my newly purchased mouthpiece with a protective flap to keep out debris… (or just a factory thing meant to be cut off before use…)

 

[johndiver999]

Well I once knew this idiot who tried to work on the second stage and used a pencil to insert the popet and the reg had spotty performance for several dives.

Upon disassembly, a big chunk of a pencil eraser was lodged in there. Then I looked on MY desk and saw the pencil with the eraser missing.

 

[axxel57]

Lever height correct.......?

 

[rsingler]

^--- This!

Pressurize the reg set and shake the S600.
Does it make no noise?
Does it quietly go "click, click"?
Does it go clackety-clack?

You're doing great! Identifying the IP and cracking effort as normal is the first step.
But barrel regs (S600) will kill you from low lever height. It's an old enough reg that the spring may have weakened. Therefore, to seal and even get 1.0", you may have had to advance the orifice enough to drop the lever. That could create exactly what you are noticing, despite a normal cracking effort.

All is not lost. You may just have to shim the spring, rather than replace it.

 

[Still Kicking]

^--- This!

Pressurize the reg set and shake the S600.
Does it make no noise?
Does it quietly go "click, click"?
Does it go clackety-clack?

You're doing great! Identifying the IP and cracking effort as normal is the first step.
But barrel regs (S600) will kill you from low lever height. It's an old enough reg that the spring may have weakened. Therefore, to seal and even get 1.0", you may have had to advance the orifice enough to drop the lever. That could create exactly what you are noticing, despite a normal cracking effort.

All is not lost. You may just have to shim the spring, rather than replace it.

What do you shim the spring with?

I love the G250 HP shims ....aka Mk25 piston bushing

 

[rsingler]

The Mk25 piston bushing is pretty thick to be used on the second stage spring. I use these instead:
McMaster 95630A217

 

[landlockeddivingdoc]

Lever height correct.......?

^--- This!

Pressurize the reg set and shake the S600.
Does it make no noise?
Does it quietly go "click, click"?
Does it go clackety-clack?

You're doing great! Identifying the IP and cracking effort as normal is the first step.
But barrel regs (S600) will kill you from low lever height. It's an old enough reg that the spring may have weakened. Therefore, to seal and even get 1.0", you may have had to advance the orifice enough to drop the lever. That could create exactly what you are noticing, despite a normal cracking effort.

All is not lost. You may just have to shim the spring, rather than replace it.

Appreciate all the insight.
I'm thinking it's the lever height-- tension seems to vary appropriately depending on adjustment knob position, and it raises/lowers appropriately when orifice adjustment tool is rotated.

During the "shake test," it's a click-click, but admittedly I've got some hearing loss. One other observation: when doing the cracking pressure testing and inhaling sloooowly, there is a palpable split second of no resistance, followed by a perception like the diaphragm smacks into the lever (this is different than my G260), then there's an appropriate resistance until cracking pressure is achieved. Would that suggest that-even at maximum adjusted height-the lever is too low, and is therefore not engaging immediately, and also not opening the valve enough, to allow appropriate airflow?

 

[rsingler]

Based on your description, you may indeed be describing the click and resistance as the plastic disc on the back of the diaphragm drops with minimal effort on gentle inhalation until it hits a low lever, and you then feel "resistance" until the valve opens ("cracks").

If you can see the lever moving as you adjust the orifice, then here's a test.
Unscrew the orifice until the lever is at its highest position. Blow through the hose connection and screw in the orifice until it seals to breath pressure.
Connect your inline adjuster and pressurize the system. It will again leak. Screw in the orifice until it just seals.
Is the lever at or below the rim of the case? Did the lever drop before it sealed? In either case, your orifice knife edge is likely scuffed (assuming you're using a new seat). If you're trying all this with the old seat, all bets are off for reasons that are multi-factorial. It might work; it might not.

If the lever is above the case rim and didn't drop before sealing, you're halfway there. Now add 1/12 turn (5 minutes on the clock face). The lever may drop 0.5mm.
Now, with the reg pressurized add the diaphragm and begin screwing on the faceplate.
If the reg begins to leak, the lever is slightly too high for the case. When the faceplate is fully screwed on, once again slowly screw in the orifice with the in-line adjuster to drop the lever until it just seals (e.g., just fits under the diaphragm). Now add 1/12 turn.

If the reg  didn't leak when you screwed on the faceplate, don't do a thing.

Now measure cracking effort and let us know.

 

[Still Kicking]

The Mk25 piston bushing is pretty thick to be used on the second stage spring.

It was kind of a joke ... because the stock G250HP came with that bushing as a shim. SP 107.00.105.